This invention relates in general to a web transport apparatus including mounted rollers for supporting a web, and more particularly to a simplified mount for a web-supporting roller which provides the axis of such roller with two degrees of freedom of movement.
Transport of an elongated flexible web along a desired path is accomplished, for example by supporting the web at various locations with rollers. With an ideal web, perfectly cylindrical rollers, and accurate roller mounting and alignment with respect to the web and each other, the web will track without lateral deviation along its roller-defined transport path. However, in practice such conditions rarely occur. Thus the transported web tends to mistrack relative to its desired path; that is, it tends to shift laterally with respect to its support rollers.
Apparatus for correction of lateral (cross-track) shifting of roller-supported webs include crowned or flanged rollers, servo actuated steering rollers, or self-activated steering rollers. In certain instances where the web is fragile, such as a dielectric web for an electrographic reproduction apparatus, crowned or flanged rollers are not suitable for use in effecting such lateral shift correction. This is because such rollers may produce undesirable distortion or concentrated loading and local stresses in the web. While servo actuated steering rollers (e.g., see U.S. Pat. No. 4,027,966 issued July 7, 1977 in the name of Jordan) or self-activated steering rollers (e.g., see U.S. Pat. No. 3,596,817 issued Aug. 3, 1971 in the name of Morse et al) have been successfully employed for correction of lateral shifting of fragile webs, such apparatus require complicated and expensive structure for mounting the web-supporting rollers.